However, as I read it, they're saying that if you just need confirmation that someone owns a particular number, they'll do that via email - usually for things like wiretaps or warrants, iirc, the LEO has to attest that they validated that so-and-so that made a harassing phone call to whoever owns number XXX-XXX-XXXX that the call originated from, ergo, this is probable cause to search them, etc.
So in this case, instead of generating a subpoena for records that a lawyer will have to review for $$$, the LEO sends an email from their work address that says, "I'm investigating Y, does So-and-so own XXX-XXX-XXXX?", bandwidth emails back with a "Yes" or "No" (obviously I assume there's a slightly more formal response for documentation purposes).
Saves legal time, doesnt' expose meaningful info, there's got to be some sort of validation step (if I emailed from a gmail account I'm sure I won't get very far, but hey, why doesn't someone try?). I don't see a huge issue here, assuming this is how it works.